(1) Field of the Invention
The present invention relates to polymerizable compositions for making polymerized thio containing resins, and in particular fast curing compositions at room temperature as well as to a polymerization process for making such thio containing resins and especially a room temperature polymerization process.
The polymerizable compositions and the polymerization process of the invention are particularly useful for making optical articles such as lenses, prisms, optical fibers, filters or for making different types of substrates, such as information recording substrates.
The polymerizable compositions and the polymerization process of the invention are also specifically suited for making various coatings and in particular coatings for optical applications.
(2) Description of the Prior Art
Plastic materials are widely used in the optical field and particularly in the opthalmic field for their lightness, high impact resistance and tintable capability by immersion in a bath containing an organic dye.
Optically transparent plastic materials having a high refractive index n.sub.D =1.6 or even higher have been developed recently which renders it possible to manufacture optical articles such as lenses of lower thickness for an equivalent corrective power (optical power).
A class of such materials is comprised of polythiourethane resins.
Polythiourethane resins for making optical lenses are described in U.S. Pat. No. 4,775,733. In this document, the polythiourethane resins are polymerized from polymerizable compositions comprising a polyisocyanate and a polythiol in the presence of a polymerization catalyst. The catalysts are tin complexes such as dibutyl tin dilaurate and the polymerization is a thermal polymerization.
Document JP-02166158A discloses a process for making polyurethane resin moulding which comprises adding in polyether polyol a thiocyanate salt such as ammonium thiocyanate or sodium thiocyanate, a crosslinking agent, catalysts and other additives and thereafter mixing with denatured diphenylmethane diisocyanate, filling into a reactant tank and injecting into a mould with heating. The catalysts are comprised of a dipropyleneglycol solution of triethylamine and dibutylene tin dilaurate.
Another class of useful materials comprises the resins obtained by polymerization of a composition of polymerizable monomers including one or more polymerizable episulfide compounds.
Episulfide compounds and their polymerization are disclosed in EP-A-761 665 and EP-A-785 194.
Unfortunately, the polymerization of these polymerizable compositions needs a long thermal cycle, generally between 8 hours to several days in order to obtain fully polymerized articles without striation or strain.